These guys are making iron from iron ore in a so-called bloomery.
For more info click below.
Carcoal is filled into the oven (bloomery) and heated up to approx. 1000-1200 °C. Then consecutive layers of iron ore and charcoal are stacked in the bloomery. The fire has to be kept going at no more than 1200°C, otherwise the iron would become runny which is actually not desired in this process.
The teperature is controlled by bellows used to blow air into the furnace. During this hour-long process, the slag becomes runny and the heavier iron particles fall to the bottom of the bloomer and stick together in a growing lump of iron.
Finally, the bloomery is opened at the bottom and the iron (bloom) is extracted.
To make the bloom more handable and to drive out the worst air bubbles inside it is immediately forged into a rough lumpy shape.
Sometimes the bloom is nicked one or two times with an axe to produce breaking points to make it easier to proces it later-on when it is fored into ingots.
Blooms like the one above, nicked, have been found in Norway for example.
For the process shown above 26 kilos of charcoal and 15 kilos of (good) mineral iron ore were used. The result was a bloom of about 6.2 kilos which is close to the actual maximum output possible. From a bloom this size a good blacksmith will forge (refine the bloom) into a useable iron ingot of about 1 kilo. For this process the bloom is split, then forged into elongated pieces and folded over in itself. This done approx. 8 times at least.

The estimated amount of work, building the oven, collecting the ore plus the actual iron making process takes the three men about 80 hours of work. (This is what the guys who did the presentation calculated). This does not include the fact that the charcoal used has to be produced first, too.